Calcining coal at high temperatures.



W. DYRSSEN.

CALCINING COAL AT HIGH TEMPERATURES.

APPLICATION FILED MAY 27, I918.

1 ,27 7,707 Patented Sept. 3, 1918.

' process.

WALDEMAR DYBSSEH, OF NEW YORK, N. Y.

CALCINING COAL AT'HIGH TEMPERATURES.

Specification of Letters Patent.

Patented Sept. 3, 1918.

Application filed May 27, 1918. Serial No. 236,866.

To all whom it may concern:

Be it known that I, WALDEMAR DYRSSEN, a subject of the king of Sweden,residing in the city, county, and State of New York, have inventedcertain new and useful Improvements in Calcining Coal at High Tem-1riieratures, of which the following is a specication. v

The pur ose of the invention is to facilitate the ca cinin of coal by anelectric furnace especially designed for such work and by a method whichprotects the charge from the air, involves hlgh efficiency and smallradiation losses, may be worked continuously and economically andoperates with 'changes of voltage within only narrow limits, or withpractically constant voltage and power.

H The accompanying drawings illustrate the furnace built according tothe invention and arranged to carry out the improved Figure 1 is avertical section;

Ffig. 2 is a horizontal section above the rec 3 is a vertical section ofa modified detail.

7 Referring now to the furnace illustrated,

- through which water is passe it is provided with a brick wall A on theoutside of which are coolin troughs B (i and with a roof C also of brickwith a charging opening lined with a water. cooling r1n D. Around thecharge opening are electro es E which penetrate the roof, these openingsin the roof also being surrounded by water cooling rings F. The bottom Gof the furnace is also of brick and water cooled and has a dischargeopening preferably in line with the charging, opening above. and formedat the lower end with a water cooled chute or cone H and a cylindricalextension J at the upper and lower end of which are located slide valvesK and L. At the top is a charging chute M which is maintainedapproximately full of crushed coal fed to it by a screw conveyer orsimilar device. From the bottom of the chute M the charge will spreadout to the walls as shown with a roughly conical upper surface leaving aspace below the roof which will save the roof and the openings throughwhich the electrodes pass from excessive heat.

The current is conveyed to the electrodes usually from a transformer, atsuitable voltages, by means of cables N and electrode holders. 0. Theupper ends of the electrodes carry screws P passing throu h handoperated nuts Q bearing on fixed By turning the nuts the electrodes maybe raised or lowered.

The product is discharged practically continuously by alternatelyoperating the valves K and L. Or a continuously operating screw S, Fig.3, driven by a motor T may be used for removing the product from thebottom of the discharge chute H.

The electric furnaces heretofore used for the calcining of coal havebeen rather crude and usually of the open-top style with electrodes invertical position entering from above and with no provision or noadequate provision for protecting the charge from air. In such furnacesthe regulation of the electric power consumed has required aconsiderable range of adjustment of the voltage. At the start, when thecharge has been cold and the electric resistance correspondingly high, ahigh voltage has been required.

And as the temperature in the charge has increased and the resistancehas been correspondingly lowered, the voltage had also to be lowered.

These difficulties are largely eliminated by the present invention.Where air has been allowed to enter it has burned the charge and theelectrodes and the resulting combustion gases have escaped at a hightemperature andwith a considerable loss of heat. The present processadmits little or no air to the charge and to the electrodes supports R.

and for this reason effects a considerable economy. With my improvedprocess the operation is easier and the output is increased by reason ofthe practically or approximately constant voltage and power consumption.The angular arrangement of the electrodes permits their lower ends to bebrought together or separated and thus to take care of the variations inresistance in the charge. At the start the ends of the electrodes can beput so close to each other that the electric energy will be consumedentirely or greatly by arcs between the ends of the electrodes and anordinary voltage can be used. As the charge and the gases in the arcbecome hotter the resistance will become less and the current taken willtend to increase, but the resistance can be increased to normal bywithdrawing the elec tively high resistance.

it is possible to regulate the input of electricpower without change ofvoltage.

Insteadof starting by bringing the ends of the electrodes close enoughtogether to strike an are directly between them, another,

and preferable, method. is to start the charge with coke between theelectrodes and to gradually displace this by coal, which has a higherresistance; using the adjustment of the electrodes for varying theresistance after the operation shall have been well started and the cokepassed below the calcining zone. j

The first small part ofthe product discharged will be coal which has notbeen well calcined or will be coke. After this coal will be fedcontinuously into the chute M as it is withdrawn from the dischargingopening. The operation will thus be continuous or practically so. Thiswill result in increased output. Also the operation will be more regularand the electric resistance will be so nearly constant as to avoid anysubstantial movement of electrodes or changes in the voltage, and a moreuniform product can be obtained.

The diverging arrangement of the electrodes, besides providing an easymeans of regulating the resistance, has also an equalizing effect on thepower input even after the charge has become hot and the desiredequilibrium is reached by withdrawing the electrodes to proper position.The resistance in the charge at the lower ends of the electrodes isconsiderably less than that of the buried portions of the electrodesabove their ends. The current will tend to go to the ends and to createthere a heat zone of practically constant resistance so that the powerconsumption is nearly steady and can be kept absolutely so with onlysmall changes in voltage. As the charge is withdrawn at the bottom andintroduced at the top practically no change in resistance will occur.The heat zone between the ends of the electrodes can be maintained at asubstantially constant temperature and the colder portion above willhave a compara- On the other hand, where parallel electrodes have beenused the conditions are less favorable because the current seeks to gothrough the charge at every point in the buried portion of theelectrodes and, since the distance between them is the same at anypoint, there is no tendency to create a distinct heat zone such as isproduced by my arrangement. With my arrangement, therefore, atransformer andother electric equipment may be used without 2. voltchanger or with a simple one having only a few. taps working withinnarrow l1mits, which is much chca er than a transformer with a widerange 0 voltage.

Radiation losses are reduced to a minimum with my arrangement. Most of.the heat is developed around the ends of the electrodes and these areburied in the-charge and located at or near the center of the furnace.The surrounding portion of the charge protects the furnace walls androof from the heat. The air space between the top of the charge and theroof and water cooling rings therein further protects these parts andinsures their durability in good condition. The passing of theelectrodes 80 through portions of the roof which are above the naturallevel of the charge, where there is no coal to heat the furnace roof toa conductive degree, saves any escape of current from the electrodes tothe roof at these points. The gases or other volatile matter dried out.of the charge take the shortest path to the outlet through the chargingchute M and thus preheat the charge passing down through this chute. Thedischarge outlet is so arranged that little or no air can passtherethrough into the furnace.

Though I have described with great par- 'ticularity a certain furnaceand mode of operation, yet it is not to be understood therefrom that theinvention is restricted to the particular furnace and method described.Separate features of the furnace and separate steps, of the process maybe used in other connectionsand the invention may be utilized not only'for calcining but also for graphitizing or otherwise treating coal andother materials without departing from the invention as defined in thefollowing claims.

What I claim is: a

1. An electric furnace for calcining coal having a roof through which isa charging opening and a bottom through which is a discharging openingfor the calcined coal and which is adapted to exclude air and havingelectrodes arranged to extend into the chargeand to produce a heatingzone in the path between said openings. I

2. An electric furnace for calcining coal having a roof, electrodesextending through 115 said roof and converging toward each other attheir ends, said furnace having a charging opening. for raw coal throughthe roof and a discharging. opening for calcined coal through the bottomso that the furnace may 120 be operated continuously.

3. The method of calcining coal which consists in embedding thereinelectrodes arranged at an angle with each other so as to be nearestto,each' other at their ends, 1215 4.-The method of calcining coal which1&6.

consists in embedding therein electrodes ar-' gitudinally to vary thedistance between ranged -'at. an angle with each other so as their endsso as to require a substantially or to be nearest to each other at theirends, approximately constant voltage for varying 10 and passing asuitable current through said conditions of the charge.

5 electrodes and feeding coal continuously In Witness whereof I havehereunto signed through the zone aboutthe ends of the my name.electrodesand adjusting said electrodes lon- WALDEMAR DYRSSEN.

copies of this patent may be obtained tor five cents each, by addressingthe Commissioner of ratentl.

Washington, D. 0.

